[PATCH, PR 49089] Don't split AVX256 unaligned loads by default on bdver1 and generic

Richard Guenther richard.guenther@gmail.com
Tue Jun 14 10:17:00 GMT 2011


On Tue, Jun 14, 2011 at 1:59 AM, Fang, Changpeng <Changpeng.Fang@amd.com> wrote:
> Hi,
>
> The patch ( http://gcc.gnu.org/ml/gcc-patches/2011-02/txt00059.txt ) which introduces splitting avx256 unaligned loads.
> However, we found that it causes significant regressions for cpu2006 ( http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49089 ).
>
> In this work, we introduce a tune option that sets splitting unaligned loads default only for such CPUs that such splitting
> is beneficial.
>
> The patch passed bootstrapping and regression tests on x86_64-unknown-linux-gnu system.
>
> Is it OK to commit?

It probably should go to the 4.6 branch as well.  Note that I find the
X86_TUNE_AVX256_SPLIT_UNALIGNED_LOAD_OPTIMAL odd,
why not call it simply X86_TUNE_AVX256_SPLIT_UNALIGNED_LOAD?

I'll defer to x86 maintainers for approval.

Richard.

> Thanks,
>
> Changpeng



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